1. Field of the Invention
The present invention relates to a continuously variable valve lift system for an engine, particularly a continuously variable valve lift system for an engine that can adjust opening/closing timings and open/close times of intake/exhaust valves according to rotation of a camshaft.
2. Description of Related Art
According to common actuating mechanism for a valve in the related art, a valve lift was only uniformly formed according to the profile of a driving cam formed on a camshaft, but it was impossible to change the valve lift and duration. Therefore, because an engine worked under a fixed valve lift and duration, it was impossible to improve the engine power and reduce fuel consumption by changing the valve lift and duration.
For this reason, studies for developing valve actuating mechanisms that can adjust the valve lift, open/close times, and opening/closing timings according to driving conditions of the engine has been conducted in recent years. One of the actuating mechanisms is a continuously variable valve lift system (CVVL), which is proposed by the present applicant.
Because the continuously variable valve lift system can adjust opening/closing timings of intake/exhaust valves and valve operations, such as a valve lift, to optimum conditions, depending on working conditions of the engine, it is possible to improve the engine power by increasing the amount of intake under high velocity and high load, and also reduce fuel consumption and exhaust gas by minimizing EGR effect or throttle loss under low velocity and low load.
However, according to continuously variable valve lift systems in the related art, a lot of components were used and the combining structures were complicated. Further, since continuously variable valve lift systems were designed to occupy the upper space higher than the camshaft in the cylinder head of the engine, total height of the cylinder head had to be increased.
Therefore, the entire size of an engine equipped with the continuously variable valve lift system had to be increased, such that the space occupied by the engine in the engine compartment was increased, which made it difficult to set a layout of other devices.
Further, there were a lot of moving components and the operational mechanism was correspondingly complicated, such that it was difficult to precisely and reliably adjust the valve lift and duration and secure sufficient durability for the entire variable mechanism of the engine equipped with the system.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.